1. Field of the Invention
This invention relates to a television device having a clock, and particularly relates to television device which is possible to set the clock to the time using the present time information included in television broadcasting signals.
2. Description of Related Art
Many clocks are provided in devices in a television to provide various conveniences in the use of a television. One example of such a convenience includes an advanced recording reservation system of a video tape recorder. A clock is provided in a video tape recorder, when a user want to record by advanced reservation the user feeds data of a channel which will broadcast a television program to be recorded and data of time when the program will start and end previously in the video tape recorder, and the video tape recorder will automatically record the reserved television program beginning from the start of the program to the end of the program based on chronometry by the clock. Some video tape recorders are structured so that regeneration operation starts automatically at the time of advanced starting reservation and stops automatically at the time of advanced stopping reservation.
In European television broadcasting, a broadcasting service, in which the starting time of a television program is interpolated in vertical interval time code as an identification code of a television program (the program identification code is referred to as a label) now being broadcasted, is practically used, and a technology in which the above mentioned label is used for advanced program reservation has been established for recording systems such as video tape recorders. More in detail, the recording system compares a label interpolated in broadcasting signal of a reserved channel with broadcast starting time data out of the advanced program recording reservation data fed by a user including data of the channel to be recorded and data of broadcast starting time data and broadcast ending time, and then the recording system operates recording during a period while the label agrees with the starting data.
Various broadcasting services, for which these advanced recording reservation technology is acceptable, such as Video Program System (called VPS hereinafter), in which the label is interpolated in the line 16 in a vertical interval time code applied in Germany, Switzerland, and Austria, and Program Delivery Control (referred to PCD hereinafter), in which a label is transmitted by using packet 8/30/format 2 of Teletext applied in the Netherlands and Dutch using area of Belgium, are practically used.
Here, Teletext is described briefly. In Teletext, data of a magazine is transmitted using packets from 0 through 29. Only magazine number 8 has packets from 0 through 30, the packet 8/30 includes not only the packet 8/30/format 2 but also packet 8/30/format 1, this type of packet is transmitted about every one second interval as service data packet of a broadcasting station. Packet X/O is defined as Page-Header of the Teletext.
For reference, signal formats of VPS, 8/30/format 2, 8/30/format 1, and Page-Header are illustrated in FIG. 11 to FIG. 14. As obvious in these figures, the label information is included in data areas in bytes from eleventh byte to thirteenth byte in the case of VPS, and other data including CNI data that is an identification code of broadcasting area and broadcasting station are transmitted.
The label information is included in data area of bytes from sixteenth byte to twenty-first byte and, the label information and also CNI data same as VPS signal are transmitted in the case of 8/30/format 2. Present time information comprising years, months, days, hours, minutes, and seconds is included in data area of bytes from fifteenth byte to twenty-first byte in the case of 8/30/format 1, and in data area of bytes from thirteenth byte to fourteenth byte NI code that is the identification code of a broadcasting station is included. In many cases for Page-Header, data area of bytes from thirty eighth byte to forty fifth byte includes the present time information comprising hours, minutes, and seconds.
The recording system applied with advanced recording reservation technology utilizing label system as described herein above is provided with a switching system in preparation for troubles such as intermittent transmission of label. In the event that the broadcasting station happens to be involved in a trouble and can not transmit the label signal, the advanced recording reservation operation of the recording system is switched based on the time of a clock in the recording system by transmitting a prescribed control signal from the broadcasting station so that the recording system records during the period of time from the programmed starting time to the programmed ending time of the television program which had been set by a user.
By the way, to operate accurately a recording based on the time of the clock, as a matter of cause, it is required that the clock is set to the correct time signal. To keep a clock in correct time, conventionally in the event of failure of power supply or of newly supplying of power to a recording system by putting a power supply plug of the recording system in a socket for commercial power supply, every time it is required to set the clock to the correct time. However, it is troublesome to set a clock to the correct time for users.
To eliminate the troublesome time setting, an automatic time setting method in which present time information included in television broadcasting signals as described in the above mentioned Teletext is utilized has been known.
When a clock incorporated in a television system is set to the correct time automatically as described herein above, it is required to select a broadcasting station which transmits television broadcasting signals interpolated with the correct present time information in the area where the television system is used.
However, depending on the area, some broadcasting stations transmit the correct present time information, though the time information could be not the full time information but the time information including only hours, minutes, and seconds as Page-Header described herein above, in such case the correct time data of years, months, and days cannot be set to the clock automatically, it is a problem. Otherwise, even in the case that the time information includes full data of years, months, days, hours, minutes, and seconds, in an area where the standard time is different from that of the transmission, the time data of only years, months, and days is acceptable, further, in an area where the date is different due to the difference in time from that of the transmission, no time data of years, months, days, hours, minutes, and seconds can be used.
Conventionally, automatic time setting to the clock has not been used in areas where they can receive only such defective time information, and only in areas where they can receive correct perfect time information of years, months, days, hours, minutes, and seconds, the automatic time setting to the clock has been accommodated using the time information interpolated in broadcasting signals.